The cryogenic treatment of heat-treated metal is a one-time, permanent process that helps to eliminate residual stresses in metal components. Residual stress in materials is caused by a variety of things, including the actual formation of the metal, machining or casting, and the heat treatment process itself. It is thought that after metal is formed and heat treated, stresses are locked-in due to the outer part of the metal cooling first, contracting, and compressing the hotter, inner material. As a result, the inner portion of the metal has a residual tensile stress and the outer portion has a residual compressive stress.
Cryogenic treatment can help reduce these residual stresses by creating a denser, smoother surface with improved material and performance properties. The process uses liquid nitrogen to reduce the temperature of heat treated parts to -300° F. The metal components are then kept at this cryogenic temperature for 24 hours. In steels, it has been documented that as carbon particles precipitate, carbides form a lattice structure and fill microscopic voids. Applications for cryo treatment include aluminum casting, optical mirrors, cutting tools, gun barrels, engine and drive components, and much more.
The benefits of using Nitrofreeze® cryo technology are fivefold.
#1 Increased Durability
Nitrofreeze® cryogenic treatment produces a more consistent granular structure for increased durability. When steels are heat treated, a percentage of retained austenite (RA) remains. The RA’s crystalline structure is less desirable than that of martensite, which is both very strong and very hard. Cryogenic treatment promotes the additional transformation of RA into martensite and further eliminates voids or imperfections in the metal’s microstructure.
#2 Improved Wear Resistance
The cryogenic process that Nitrofreeze® uses improves wear resistance by increasing the carbon content in the steel. Among metallurgists, it’s well known that steels with greater carbon content (such as tool steels) are both harder and stronger. When steel parts are cryogenically treated, the precipitation of eta-carbides modifies the metal’s carbon structure for greater wear resistance. As scanning electron microscopy (SEM) shows, the number of black and white eta-carbides is increased.
#3 Reduced Fatigue Failure
The stress relief that Nitrofreeze® cryogenic treatment provides reduces fatigue failure, the formation and propagation of cracks due to repetitive or cyclic loads. From the moment a metal changes from a molten mass to a solid form, stresses are created. Manufacturing processes such as machining and grinding also add stress. Because these combined stresses form areas that are prone to cracking, Nitrofreeze® cryogenic treatment attacks the root cause of fatigue failure.
#4 Proven Quality
Nitrofreeze® cryogenic treatment is quality-driven from start to finish. From the time your parts arrive at our facility through final inspection, trained technicians ensure the success of your project. Nitrofreeze® validates all of our cryogenic treatment cycles to determine that all process parameters have been met and includes a statement of compliance with all standard orders. For a nominal fee, we can also provide you with a Certificate of Compliance.
#5 Consistency and Flexibility
Nitrofreeze® uses a proprietary cryogenic treatment process with ultra-slow ramp rates and stabilization stops, the industry’s longest holds at -300° F, and minimum 24-hour dwell at temperature. Because our Worcester, Massachusetts (USA) facility is well-equipped, we can meet your volume requirements and cryogenically treat parts of almost any size or weight. For advanced applications, we offer custom cryogenic profiles and can develop a custom profile that’s based on your specific needs.
Choose Nitrofreeze® Cryogenic Treatment for Heat Treated Metal
Do you work with heat treated metal parts? Nitrofreeze® cryogenic treatment increases durability, improves wear resistance, reduces fatigue failures, ensures quality, and offers both consistency and flexibility. If your heat treated part is a viable candidate for cryogenic treatment, we can perform sampling to demonstrate our process. The consultation is free of charge and turnaround times average two business days. To get started, contact us at the phone number and email listed below.
(508) 459-7447 x109 | email@example.com